/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements. See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership. The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the  "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
/*
 * $Id$
 */
package wx.xml.xalan.xalan.templates;

import javax.xml.transform.TransformerException;

import wx.xml.xalan.xalan.transformer.TransformerImpl;


/**
 * Implement an unknown element
 *
 * @xsl.usage advanced
 */
public class ElemUnknown extends ElemLiteralResult {
    static final long serialVersionUID = -4573981712648730168L;

    /**
     * Get an int constant identifying the type of element.
     *
     * @return The token ID for this element
     * @see wx.xml.xalan.xalan.templates.Constants
     */
    public int getXSLToken() {
        return Constants.ELEMNAME_UNDEFINED;
    }

    /**
     * Execute the fallbacks when an extension is not available.
     *
     * @param transformer non-null reference to the the current transform-time state.
     * @throws TransformerException
     */
    private void executeFallbacks(
        TransformerImpl transformer)
        throws TransformerException {
        for (ElemTemplateElement child = m_firstChild; child != null;
             child = child.m_nextSibling) {
            if (child.getXSLToken() == Constants.ELEMNAME_FALLBACK) {
                try {
                    transformer.pushElemTemplateElement(child);
                    ((ElemFallback) child).executeFallback(transformer);
                } finally {
                    transformer.popElemTemplateElement();
                }
            }
        }

    }

    /**
     * Return true if this extension element has a <xsl:fallback> child element.
     *
     * @return true if this extension element has a <xsl:fallback> child element.
     */
    private boolean hasFallbackChildren() {
        for (ElemTemplateElement child = m_firstChild; child != null;
             child = child.m_nextSibling) {
            if (child.getXSLToken() == Constants.ELEMNAME_FALLBACK)
                return true;
        }

        return false;
    }


    /**
     * Execute an unknown element.
     * Execute fallback if fallback child exists or do nothing
     *
     * @param transformer non-null reference to the the current transform-time state.
     * @throws TransformerException
     */
    public void execute(TransformerImpl transformer)
        throws TransformerException {


        if (transformer.getDebug())
            transformer.getTraceManager().fireTraceEvent(this);

        try {

            if (hasFallbackChildren()) {
                executeFallbacks(transformer);
            } else {
                // do nothing
            }

        } catch (TransformerException e) {
            transformer.getErrorListener().fatalError(e);
        }
        if (transformer.getDebug())
            transformer.getTraceManager().fireTraceEndEvent(this);
    }

}
